Wireless communication systems which recently have been widely used include a mobile communication system developed on the basis of the circuit communication to provide a voice service, and a wireless packet communication system developed on the basis of on the data communication. The mobile communication system has developed from a type that provides mostly a voice service to a type that supports packet-type data by accepting demands for a packet service, which have advanced since the third-generation (3G) mobile communication system was adopted.
In particular, the packet-type data have a larger variability in data transmission rate than circuit-type data based on the voice. Furthermore, the packet-type data are transmitted at high data transmission rates. Therefore, demand for an effective transmission method of packet-type data is rapidly increasing.
To satisfy such demand, the 3rd Generation Project Partnership (3GPP) which establishes the standards of mobile communication systems has adopted a standard for providing a downlink packet service in High-Speed Downlink Packet Access (HSDPA). Furthermore, Telecommunications Industry Association/Electronic Industries Alliance (TIA/EIA) has adopted a standard for providing a downlink packet service through 1xEV-DO and 1xEV-DV.
In the packet service provided by the mobile communication system, codes and times are allocated as resources to transmit packets. Therefore, traffic variability on a time domain is much larger than in a circuit-mode allocation rule. For example, a large amount of traffic is transmitted while packets are transmitted. However, when packets are not transmitted, traffic may be not generated at all. That is, the voice communication and the packet communication may be compared as follows. In the voice communication, constant resources (codes and times) should be allocated at all times while the communication is performed. In the packet communication, however, a large amount of data to be transmitted may burst in most cases.
Meanwhile, with the development of the mobile communication system, a method for deploying and operating a base station has developed from a conventional method in which a base station is deployed in terms of the coverage of the base station to a method in which a macro base station and a micro base station are combined. That is, the macro base station is deployed to secure coverage, and the micro base station is deployed to expand the coverage and improve transmission efficiency.
To support such a development trend, a Closed Subscriber Group (CSG) base station is defined in the 3GPP Long-Term Evolution (LTE) standard. The CSG base station corresponding to the micro base station is a base station which may be applied to maintain communication in a limited area such as office or basement, which is not included in the coverage of the macro base station, like a repeater. The CSG base station may be divided into an Allowed CSG (hereafter, referred to A-CSG) base station which allows only specific mobile stations to have access and a Non-allowed CSG (hereafter, referred to N-CSG) to which all mobile stations may access. Currently, the A-CSG base station is proposed in a standardization step such that it may be deployed in the coverage of the macro base station so as to be used for indoor service operation.
The micro base station considered in the 3GPP may be roughly divided into three types, that is, a repeater, an N-CSG base station, and an A-CSG base station. The repeater expands the coverage by simply providing transmission and reception. The N-CSG base station not only expands the coverage but also improve transmission efficiency in the entire coverage. The A-CSG base station allows access of only specific mobile stations to distribute a traffic load of the network, thereby improving transmission efficiency. In addition to such a division, other divisions may be applied.
Meanwhile, other mobile communication systems such as Mobile WiMax based on IEEE 802.16 also provide methods for effectively performing communication through the combined base station operation as described above.
Therefore, considering an explosive increase of Access Points (APs) of WiFi, it is expected that the number of micro base stations which are to be deployed afterwards will increase incomparably than the number of macro base stations. For example, it may be assumed that a family registers terminals supporting the 3GPP LTE, such as a notebook computer, a cellular phone, and a PDA to an A-CSG base station and then uses the terminals. In this case, the corresponding A-CSG base station may be deployed at a specific position within an indoor environment. When it is assumed that such a base station is installed in each house in a highly developed city, the number of base stations will explosively increase.
Such micro base stations of which the number will increase explosively may transmit and receive data with smaller power than macro base stations. However, as the number of micro base stations to be deployed increases, the overall power consumption may not only increase, but the power consumption of the micro base station in each indoor environment may also increase. Therefore, a technology development for reducing the power consumption is required for the micro base stations.
As a part of the technology development for reducing the power consumption, methods for providing optimal scheduling and effective power control through a multi-hop relay system or distributed antenna system have been proposed. However, such methods have been developed to reduce power consumption during communication. Therefore, in the communication system of which the traffic variability increases in the time domain, a reduction effect of power consumption is not significant.
As for the conventional method for operating micro base stations as described above, the methods for reducing power used during the communication are reflected. However, predetermined power or more may be unnecessarily consumed even in a section in which communication is not actually performed and which occupies most part of the time domain. Therefore, the reduction effect of power consumption is inevitably limited. Accordingly, there is demand for a method and apparatus for maximizing the reduction effect of power consumption through the effective operation of micro base stations in a state in which the communication is not performed.